Answers to Your Questions About Brain Injury

Scientists and doctors have only just begun to unravel the mysteries of brain injuries. Here, some of the country's leading experts answer your questions about brain trauma.

What is brain damage? Are there different kinds?

There are many different kinds of brain damage. Neurons can be damaged directly and killed. There can be tearing and shearing of the axons, white matter connections between areas, often seen in closed-head injuries. Swelling applies pressure on the brain that can kill neurons. Loss of oxygen kills neurons, and selectively affects different areas first.

- Susan Bookheimer, Brain Mapping and Research Institute, UCLA

Are certain areas of the brain more important than others for survival? Why?

The brain stem controls regulatory functions like breathing, heart rate. These functions are critical for survival. The cortex is less necessary for survival, but is very important for making us the individuals that we are. Thus, it is possible to have an intact brain stem in a living person but very little else if the cortex is not functional.

- Susan Bookheimer, Brain Mapping and Research Institute, UCLA

How durable is the brain? How much trauma can it take?

This depends on a lot of factors. For a first injury in a young person, where there isn't gross damage such as large tissue destruction, removal or brain stem damage, or no loss of oxygen to the brain, there is a remarkable ability to improve.

But many factors can reduce the potential for recovery. Bleeding in the brain stem, large mass effects such as the massive intracranial bleeding of Ariel Sharon, the need for surgery to remove pieces of brain, and most important loss of oxygen due to substantial blood loss, all are bad signs. For someone with a previous head injury, even a small bump can have huge effects, as the brain may have already used up its "reserve."

- Susan Bookheimer, Brain Mapping and Research Institute, UCLA

Humans can tolerate very little acceleration/deceleration injury, because of the large brain size, its softness, and our upright posture. Think of a heavy, soft fruit on a branch that gets a hit. In contrast, think about the woodpecker -- that little guy gets thousands of hits to the head and doesn't miss a beat. Or how about bighorn sheep in the rutting season -- these animals have adapted by developing a complex cranial anatomy to hold the brain in the skull, like a walnut in its shell, so it can't move with even large force impacts.

How difficult is it to rehabilitate the brain? Meaning can you re-create ability or function that is lost?

Each case is unique. While most mild traumatic brain injury patients fully recover, many suffer persisting cognitive disabilities, such as loss of memory and poor concentration, even with rehabilitation. In general, the more severe the initial injury, the less likely the patient will fully recover with rehabilitation. However, even some severe brain injury patients can ultimately return to normal life after rehabilitation despite extensive damage to the brain.